Hydraulic Die Cushion Pressure Control for Surge Suppression
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Solution Overview
Problem
Die cushion devices using hydraulic cylinders face issues with surge pressure generation during press molding, which affects molding precision due to the compressibility of hydraulic oil, and existing solutions struggle with pressure adjustment and precise position control.
Innovation Solution
A control device adjusts the number of rotations of the hydraulic pump based on detected hydraulic oil pressure to manage flow rate and pressure, using a relief valve to return excess oil to the tank and reversing the pump when surge pressure is detected, ensuring accurate and rapid pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a hydraulic cylinder is used to replace an air-type die cushion device, then the device size is reduced and position control precision is improved, but surge pressure is generated during press molding which adversely affects molding quality
Solution Approach 1:
The control device predicts the occurrence of surge pressure based on press molding conditions and proactively adjusts the hydraulic pump's number of rotations before surge pressure actually occurs. This preliminary action prevents surge pressure generation while maintaining the benefits of hydraulic cushioning.
Solution Approach 2:
The system uses pressure sensors to detect hydraulic oil pressure in real-time and feeds this information back to the control device. The control device continuously adjusts the hydraulic pump's rotations based on this feedback to maintain stable pressure and suppress surge pressure during press molding.
2Object-affected harmful factors
If pressure control is achieved using a relief valve, then surge pressure can be released, but the response speed is insufficient to suppress surge pressure effectively
Solution Approach 1:
The system replaces the purely mechanical relief valve with an electro-hydraulic control system. The control device uses electrical signals to adjust the hydraulic pump's number of rotations, providing much faster response speed compared to mechanical relief valve operation. This substitution enables proactive surge pressure suppression rather than passive relief.
Solution Approach 2:
Instead of waiting for surge pressure to build up before acting (as the relief valve does), the control device predicts surge pressure occurrence and adjusts the pump rotations in advance, achieving faster effective response by preventing surge pressure rather than reacting to it.
3Measurement precision
If the hydraulic pump operates at high speed to respond to pressure changes, then pressure control accuracy is improved, but heat generation increases
Solution Approach 1:
The system dynamically adjusts the hydraulic pump's number of rotations based on real-time pressure conditions and predicted surge pressure risks. The pump operates at variable speeds rather than constant high speed, maintaining pressure control accuracy while reducing unnecessary high-speed operation that generates heat.
Solution Approach 2:
The control device continuously monitors hydraulic oil pressure and uses this feedback to adjust pump rotations optimally. This ensures the pump operates at the minimum necessary speed to maintain pressure accuracy, avoiding excessive speed and heat generation while still achieving precise pressure control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively suppresses surge pressure in hydraulic cylinders, maintaining precise control over die cushion pressure and preventing heat generation in the relief valve, thereby enhancing molding precision and reducing device size.
Implementation Method 1
a hydraulic cylinder 10 that vertically moves a cushion pad 14; a hydraulic pump P that supplies hydraulic oil from an oil tank T to the hydraulic cylinder 10
Implementation Method 2
a relief valve 20 that returns hydraulic oil discharged from the hydraulic cylinder 10, to the oil tank T
Implementation Method 3
a pressure sensor PS that detects a hydraulic oil pressure, which is a die cushion pressure of the hydraulic cylinder 10
Implementation Method 4
when a surge pressure is generated in the hydraulic cylinder 10 during press molding, the control device 40 reverses a rotation direction of the hydraulic pump P
Data Source
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AI summary
A die cushion device includes: a hydraulic cylinder (10) that vertically moves a cushion pad (14); a hydraulic pump (P) that supplies hydraulic oil from an oil tank (T) to the hydraulic cylinder (10); a relief valve (20) that returns hydraulic oil discharged from the hydraulic cylinder (10), to the oil tank (T); a pressure sensor (PS) that detects a hydraulic oil pressure, which is a die cushion pressure of the hydraulic cylinder (10); and a control device (40) that controls a flow rate and a pressure of hydraulic oil supplied from the hydraulic pump (P) to the hydraulic cylinder (10). The control device controls the number of rotations of the hydraulic pump (P) such that the hydraulic oil pressure detected by the pressure sensor (PS) reaches a die cushion pressure command value, and when a hydraulic oil pressure detected by the pressure sensor is equal to or higher than a set pressure of the relief valve (20), the control device (40) reversely rotates the hydraulic pump (P).